org.cloudgraph.store.service.CreatedCommitComparator Maven / Gradle / Ivy

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/**
 * Copyright 2017 TerraMeta Software, Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.cloudgraph.store.service;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.plasma.sdo.PlasmaChangeSummary;
import org.plasma.sdo.PlasmaType;
import org.plasma.sdo.core.CoreDataObject;

/**
 * Comparator which imposes a commit ordering on created objects based on
 * singular relations between the types for the given source and target data
 * objects. Singular relations across any number of "hops" between the 2 types
 * are detected and the "parent" types are ordered first. Where the types are
 * the same, singular relations may still exist from/to the same type forming a
 * "recursion" and these are detected by finding singular linkages between
 * between the given data objects. Note: this comparator imposes orderings that
 * are inconsistent with equals.
 */
public class CreatedCommitComparator extends CommitComparator {

  private static final long serialVersionUID = 1L;
  private static Log log = LogFactory.getFactory().getInstance(CreatedCommitComparator.class);

  @Override
  public int compare(CoreDataObject source, CoreDataObject target) {

    PlasmaType targetType = (PlasmaType) target.getType();
    PlasmaType sourceType = (PlasmaType) source.getType();
    PlasmaChangeSummary changeSummary = (PlasmaChangeSummary) source.getDataGraph()
        .getChangeSummary();
    int targetDepth = changeSummary.getPathDepth(target);
    int sourceDepth = changeSummary.getPathDepth(source);

    if (targetType.getQualifiedName() != sourceType.getQualifiedName()) {
      if (log.isDebugEnabled())
        log.debug("comparing types: " + sourceType.toString() + " / " + targetType.toString());

      if (isSingularRelation(source, target)) { // source is less than
        // target
        if (log.isDebugEnabled())
          log.debug("(return -1) - singular relation from source: " + sourceType.toString()
              + " to target: " + targetType.toString());
        return -1;
      } else if (isSingularRelation(target, source)) { // source is
        // greater than
        // target
        if (log.isDebugEnabled())
          log.debug("(return 1) - singular relation to target: " + targetType.toString()
              + " from source: " + sourceType.toString());
        return 1;
      } else {
        if (log.isDebugEnabled())
          log.debug("(return 0)");
        return 0;
      }
    } else {
      if (log.isDebugEnabled())
        log.debug("comparing data objects: " + source.toString() + " / " + target.toString());
      // give precedence to reference links, then to
      // graph path depth
      if (hasChildLink(source, target)) {
        if (log.isDebugEnabled())
          log.debug("(return 1) singular link from : " + source.toString() + " to: "
              + target.toString());
        return 1;
      } else if (hasChildLink(target, source)) {
        if (log.isDebugEnabled())
          log.debug("(return -1) singular link from : " + target.toString() + " to: "
              + source.toString());
        return -1;
      } else {
        // For say a root object which is part of
        // a tree, where the property e.g. 'parent'
        // is null the above link check won't apply,
        // Therefore rely on graph depth
        if (sourceDepth < targetDepth) {
          if (log.isDebugEnabled())
            log.debug("depth: " + sourceDepth + " / " + targetDepth);
          return -1;
        } else if (targetDepth < sourceDepth) {
          if (log.isDebugEnabled())
            log.debug("depth: " + targetDepth + " / " + sourceDepth);
          return -1;
        } else
          return 0;
      }
    }

  }

}